Washington state's I-502 marijuana legalization, taxation, and regulation initiative appears headed for victory with increasing support, according to the latest KCTS 9 Washington Poll, released Thursday. The poll had support among likely voters at 55.4% in surveys conducted during the second half of October, compared to 47.1% in surveys conducted in the first half of the month.

Similarly, opposition to I-502 was declining, from 40.1% earlier in the month to 37.6% in the second half of the month. The figures suggest that undecided voters have been breaking in favor of the initiative.

The 55.4% support figure includes 48.7% who are "certain yes" voters, 4.3% who are "yes -- could change," and 2.8% who are "undecided -- leaning yes." The 37.6% "no" figure includes 35.5% "certain no" voters, 1.6% "no -- could change," and 0.5% who are "undecided -- leaning no." Some 6.8% of voters remained truly undecided, while 0.3% said they would not vote on I-502.